TRACING THE SECRET OF EPIDEMICS.

Press, Volume LVIII, Issue 17632, 8 December 1922, Page 7

TRACING THE SECRET OF EPIDEMICS.

(By a Physician.) There is at present being carried on in London one of the most remarkableexperiments which science has ever conceived. This is the study of epidemics of disease in a large population—of mice. Just as the problems of designing a great ship are worked out on a tiny model, so the problems of vast waves of disease, affecting whole continents, are being studied in a room or two. Dr W. W. C. Topley, whose idea the "mouse population" is, has already come upon some remarkable new facts. By far the most interesting of these is the strange effect on the mouse colony of immigration into it. As soon as a number of new mice arrive trouble may be expected. I The reason, apparently, is that n 1 copulation which does not move about establishes a kind of "working agreewith its besetting sicknesses, j These are present, but they do not atthe moment newcomers arrive the agreement is upset. For these newromera are not m exactly the same nhvsical condition as the natives: some of them,, at any rate, are more liable i ll they begin to spread

their illness at once, because disease grows more active and dangerous with each new individual it attacks. Very soon a great part of the population is "down." Then, provided no fresh arrivals take place, a new "working agreement" is reached and the epidemio passes away. Here, obviously, is a real explanation at last of the outbreaks of disease which always accompany a war. No matter what care may be taken by the Army doctors, epidemics are sure, sooner or later, to arise when vast bodies of men are "on the move-" The importance of this work for farmers and stockbreeders is obvious. At present they suffer great losses which, it would seem, knowledge of these _ Gtudies of mioe might save them. Incidentally we are learning'how very complicated is the problem of defence against disease. The old idea that if only we could rid the world of germs we should be safe is seen now to belong to the "Walrus and the Carpenter" period of bacteriology when: "They wept like anything to see Such quantities of sand." Germs are everywhere in numbers greater even than the sarfij of the sea. But they are not dangerous except in certain special conditions. Only when man grows restless and begins to move in his thousands across the face of the earth does disease obtain its opportunity. At present we are without light on the means of avoiding these ill consequences of our migrations. But thu study is still only in its infancy.